| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-strength steel sheet superior in formability for an extension flange and fatigue characteristics. SOLUTION: This high-strength steel sheet comprises, by mass%, 0.03-0.10% C, 0.08-1.5% Si, 1.0-3.0% Mn, 0.05% or less P, 0.002-0.02% S, 0.0005-0.01% N, 0.01% or less acid-soluble Al, less than 0.008% acid-soluble Ti, 0.0005-0.04% in total of one or two elements of Ce and La, and the balance iron with unavoidable impurities; and contains inclusions therein which have circle-equivalent diameters of 1μm or larger and are drawn into a ratio of longer diameter/shorter diameter of 5 or more, so as to occupy 20% or less of all inclusions existing in the steel sheet by the number of pieces. COPYRIGHT: (C)2007,JPO&INPIT
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